The cost price of $40$ articles is the same as the selling price of $25$ articles. Find the gain percent. (in $\%$)

$A$ and $B$ started a business by investing $Rs. 3,50,000$ and $Rs. 1,40,000$ respectively. $A$ gets $20\%$ of the yearly profit for managing the business. Thereafter,the profit is divided in the ratio of the capital. If $A$ receives totally $Rs. 38,000$ more than $B$ at the end of a year,then the total profit is (in $Rs.$)

$A$ product when sold with $10 \%$ rebate on the listed price gave a profit of $Rs$ $70$. What was its cost price? (in $Rs$)

$A$ shopkeeper sold an article at the rate of $Rs. 35$ per article and earned a profit of $40\%$. At what price should each article have been sold to earn a profit of $60\%$?

Oil equal to $20 \%$ of the weight of groundnut is extracted in a mill. The matter left after extraction is sold as cattle feed at the rate of $Rs. 12.5$ per $kg$. The groundnuts are bought at $Rs. 20$ per $kg$ and the processing cost is $Rs. 5$ per $kg$. At what price ($Rs.$ per $kg$) should the oil be sold to earn $20 \%$ profit on total costs (Total cost $=$ cost of groundnuts and processing costs)?

$A$ shopkeeper mixes $26 \, kg$ of wheat which costs $Rs. 20$ per $kg$ with $30 \, kg$ of wheat which costs $Rs. 36$ per $kg$ and sells the mixture at $Rs. 30$ per $kg$. Find the profit percent. (in $\%$)